WS20.1 Structure–activity relationship for OligoG-induced normalization of the CF mucus phenotype

Abstract

Objectives Cystic fibrosis (CF) is caused by nonfunctional ion transport via CFTR. In the lungs insufficient clearance of mucus leads to lung infections and tissue damage. We have previously shown that the gel-forming MUC2 mucin is packed in an orderly way that allows unpacking by calcium chelation and increased pH. Using an explant system of mouse ileum, we found that in contrast to normal mucus, the mucus is attached to the epithelium in CF mice and was normalized by apical application of 100 mM bicarbonate. OligoG CF-5/20 is derived from polymeric sodium alginate comprising mainly guluronate and some mannuronate, capable of chelating calcium. OligoG is in clinical trials as inhalation therapy in CF patients. Methods Explants from the small intestine of CF mice were mounted in the horizontal Ussing-type chamber. Alginate at different concentrations or composition was added to the apical buffer, pH 7.4. The attachment of the already formed mucus was assessed by comparing the total mucus thickness before and after aspiration. Results OligoG at 1.5% or higher normalized the mucus phenotype without increase in mucus thickness. The alginate fraction containing 12 guluronate units was most effective, whereas shorter and longer molecules were less efficient. Mannuronic polymers were inactive. Conclusion These results suggest that it is guluronic acid and its calcium chelating capacity that is the important and active component in OligoG. These observations indicate that OligoG could act by normalizing the mucus layers in both the intestine and potentially the lungs of cystic fibrosis patients at therapeutically relevant concentrations.